Process for obtaining improved shellac compositions for molding



Patented Mar. 12, 1935 I t UNITED STAT Es PAT ENT oF cs I ;1,994,071 y;p I

I 7 PROCESS FOR'OBTAININGIMPROVED snnn- V V LAC COMPOSITIONS non MOLDING William Howlett Gardner,iNew York,'N. Y, I NoDrawing. Application October 22; 1932,

p SeriaLNo. 639,042

2 oi iinsi. (01.106522; i

The principal object of this invention relates dered plastic by heating them on a steam table. to a process whereby an improved composition Pieces of sufficient size to fill the mold are then i btained for plastic molding purposes which cut with a knife, and the articles molded under gives articles having greater resistance to warppressure in a case-hardened steel die. The hy- 5 ing-anddeformation at high temperatures, "and draulic-press is water cooled during this opera- ,5

yet retains the mechanical and physicalproption. When 'sufliciently cool to be handled witherties of the present. products; out distortion, the'pressure isreleasedandthe Shellac was one of the first substances used finished art cle removed. as a base in plasticcomposition. Because of its For large pieces the shellac and filler in a wide use 'in this and the spirit varnish fields, plastic condition are-forced by pressure into the 1 it has become customary to classify as shellac mold. This is known as extrusion. substitutes many resins which in their physical In either case it can be readily seen that little and chemical properties have, little or no reopportunity is afiorded for polymerization and semblance to shellac. The aldehyde-phenol condensation of the shellac to take place or to l5 resins when soluble in alcohohhave frequently obtain articles highly resistant to heat def- 45 rolls maintained at a temperature sufficient to been so classed. These resins lack many of the ormation. However, I have found that it'is mechanical and physical properties inherent in both economical and practical to subject the shellac and since there is a very marked di-. slabs or biscuits to a baking process prior to ference in rate and manner of polymerization molding in order to accomplish this result. Ben- 0 or cure, the mechanical processes employed in eficial condensing agents such as dioyandiamide, manufacturing articles from the two types diiphthalic anhydride, sulfanilic acid, such as defer. Because of the relatively low softening or scribed in my. co-pending applications as confusion temperatures of the usual shellac comtaming tWO mo e active chemical groups may positions, aldehyde-phenol resins have supplantbe incorporated in the composition with imed shellac for certainspecific uses in spite of proved results. The material resulting from the 25 the fact that they may be inferior in other propbaking process may then be molded while still erties. plastic, or it may be cooled and stored for use.

For certain engineering uses the softening or I de i d, the Slabs m y be broken up and the deformation temperature of a molded article is composition ground and molded in powdered very important. In order to meet specifications form y the use Of a hot mold and Subsequent 30 1 in such cases it was necessary to subject the cooling of the art in the the T0 y w shellac article to a prolonged heat treatment. d this is the first time a Successful b k This for most cases has hitherto ploVen to p s a b mp y d w h sh ac c mbe impractical. Prolonged application of heat positions Prior to melding o the articleswith the subsequent cooling in the mold so slows Since sh l a mp s t s v y Wi y in ha 35 up production that the cost is prohibitive. Bakacter from all aldehyde-p resinv p ing finished articles will cause warping and distions, it is not necessary to add any plastic tortion, and in many cases the structure is weaksolvent or condensing agents in order to be able ened through e formation of blisters from to mold the composition resulting from the heat 40 Water which is e v during the baking pr0e treatment process such as is required when using aldehyde resins (U. s. Patent 1,146,388) but be- In the manufaPturP she mfflded artlcles, cause of the totally different thermo-plastic gi zfigfig g figi zg gg 5 1 airmum characteristics of shellac a wide variety of chemg S e Wem hot 'icals, such as those described in my co-pending applications, ranging from strong acids to strong bases can be added to obtain the marked beneficial results.

keep the shellac in a moltenstate. The mixture'is repeatedly repassed between the rolls 1 until the filler has become thoroughly wetted with the molten shellac and has a uniform composi Unlike aldehyde-phenol resins, shellac remains tion. The resulting plastic mass is then pressed plastic for relatively long period of time, 50

into slabs or biscuits, and may be allowed to cool i polymerization and condensation, so that and storeduntil desired for molding. If colored by Proper control of the baking process it is objects are required, thecoloring material is not necessary to pl blank ms o t is added in the original mixture. process, since the trimmings can beneficially be Before molding the slabs or biscuits are renadded to the original mixture of ingredients 55 employed in preparing the composition prior to baking.

As examples of my invention, I cite the following:-

Example 1.-A mixture of nine pounds of asbestos and three pounds of shellac is thoroughly mixed, as by passing between hot rolls maintained ata temperature suflicient to keep the shellac molten, until the, composition is uniform. The plastic mass is then pressed into sheets or slabs and these are subjected to heat at 300 F. for a period of hour. The slabs or sheets are then formed into units adapted for reception by molds, or, they may be cooled and comminuted, as, for example, ground to powdered form. The comminuted mixture may readily be placed in molds and pressed into forms in the usual manner.

Example 2.A mixture of nine pounds of aspounds of shellac and one ounce of bestos, three dicyandiamide is repeatedly passed between hot rolls maintained. at a temperature suflicient to keep the shellac molten, until the composition has a uniform distribution. The plastic mass is then pressed into slabs and these are placed in an indirect heating oven at 293 F. The oven is maintained at this temperature and the composition subjected to a bake of one-half hour.

The slabs are then cut into shape and size suitable for filling the mold. The article is formed in the mold by subjecting this material to 2700 pounds per square inch pressure in a water cooled hydraulic press. Conditions may be varied Widely. In this application, shellac refers to all forms of lac, products prepared from the secretion. of. the lac insect.

Having described my invention, what I claim, and desire to secure by Letters Patent, is as follows:

1. The process of forming a shellac composition adapted for use in plastic molding, which consists in preparing an intimate mixture of shellac and a filler, then subjecting the said mixture to a baking process conducted at atmospheric pressure securing the major part of condensation of the shellac.

2. The process of forming a shellac composition adapted for use in plastic molding, which consists in preparing an intimate mixture of shellac and a filler, then subjecting the said mixture to a baking process conducted at atmospheric pressure securing the major part of condensation of the shellac, and thence forming the treated composition into units adapted for reception by molds.

WILLIAM HOWLETT GARDNER. 

